1. Field of the Invention
The present invention relates to an apparatus and process for detecting foreign materials and, more particularly, to an apparatus and process for detecting foreign materials for use in LSI manufacturing processes.
2. Description of the Related Art
FIG. 2 shows a schematic perspective view illustrating a conventional apparatus for detecting foreign materials. In this figure, a chemical specimen 1 flows through a container in the form of a transparent pipe 2. An observation region 3 for the chemical specimen 1, as illustrated partially cutaway, is irradiated with a laser beam 4 such as an He-Ne laser beam through a projection optical system 5. The scattered light of this laser beam 4 is formed into an image at an image-formation region 7 through a receptor lens system 6.
In a conventional apparatus for detecting foreign materials of this type, the chemical specimen 1 enters the observation region 3 through the transparent pipe 2 and circulates through a return passage which is not illustrated. The observation region 3 is irradiated with the laser beam 4 through the projection optical system 5 and the laser beam 4 passes through the chemical specimen 1.
When foreign materials exist in the chemical specimen 1, the laser beam 4 is diffused to form scattered light. This scattered light is projected on image-formation region 7 through a receptor lens system 6. The foreign materials have been detected by monitoring the scattered light.
In the above apparatus for detecting foreign materials, since a laser beam is used, a transparent pipe 2 must be employed. Accordingly, it is difficult to employ this apparatus when the chemical specimen 1 is a photosensitive substance such as a photoresist.